1. Field of the Invention
The present general inventive concept relates to a color correction apparatus usable in a scanner and a method of controlling the same, and more particularly to a color correction apparatus usable in a scanner which can change data existing outside of a gamut boundary to correct data existing within a gamut boundary, and a method of controlling the same.
2. Description of the Related Art
Conventional color I/O (Input/Output) devices (e.g., cameras, scanners, monitors, and printers) have different color spaces according to their categories. For example, a conventional color printing device uses a CMY color space. The color CRT monitor or the computer graphic device uses an RGB color space. In order to reproduce colors of the above-mentioned devices having different color spaces, a variety of objective information (i.e., CIE color space for numerically expressing the colors) associated with the colors to be actually reproduced is typically used, for example, CIE-XYZ, CIE-Lab, and CIE-Luv.
The color I/O devices have different gamuts (i.e., different color ranges) in addition to the different color spaces. Due to a difference between the gamuts, although the same image is observed by different I/O devices, different images are created by the I/O devices. Therefore, there is needed a new method for correctly describing the gamut to implement the correct matching of the gamuts of the color I/O devices, and correcting input colors on the basis of the described gamut.
The color correction is indicative of the conversion of the color space of the input color signal. In more detail, the color correction converts a device-dependent color space (e.g., RGB and CMY) of the input color signal into a device-independent color space (e.g., CIE-XYZ and CIE-Lab). In order to convert the device-dependent color space into a device-independent color space, the scanner manufactures the lookup table for the color correction, so that it uses the lookup table to correct the color.
In order to manufacture the lookup table for the color correction of the scanner, a conventional method acquires RGB data of all the patches existing in the color chart by scanning the calibration color chart such as IT8.7/2, and performs the color-measurement of the calibration color chart using the color-measurement device, so that it acquires Lab data of all the patches contained in the color chart.
In this case, “L” is indicative of a brightness, a horizontal axis of the coordinates is denoted by “a”, a vertical axis of the coordinates is denoted by “b”, “a+” is a Red-direction, “a−” is a Green-direction, and a “b+” is a Yellow-direction, and “b−” is a Blue-direction. The center location (a=0 and b=0) corresponds to an achromatic color. If the color has the L value of 100, this color indicates a pure white color. If the color has the L value of 0, this color indicates a black color. As the “a” and “b” values of the color increase, the color becomes more distant from the center point, and the chroma value becomes higher, so that this color is considered to be a clear color.
As illustrated in FIG. 1, the Lab data of all the patches existing in the acquired color chart must exist in the range of 0≦L≦100, −128≦a≦128, and −128≦b≦128.
Thereafter, a color characteristic equation is calculated using the acquired RGB and Lab data. The Lab data of all the RGB data is calculated on the basis of the calculated color characteristic equation, so that the lookup table for the color correction is manufactured.
However, the above-mentioned conventional method for manufacturing the lookup table for the color correction statistically analyzes the RGB data and the calculated Lab data, and calculates the color characteristic equation on the basis of the statistically-analyzed result, so that the gamut may unavoidably and undesirably fall out of the range of 0≦L≦100, −128≦a≦128, and −128≦b≦128, due to an extrapolation error.
As a result, the above-mentioned conventional method is unable to correctly describe the gamut, so that it can effectively correct the color of the scanner.